There has been marked progress in the storage capacity of conventional magnetic recording devices. The size of recording and reproduction heads has been reduced over time and there have been improvements in the uniformity of media, among other advancements. In order to accurately read smaller-sized magnetic data recorded on media, improvements have continued into reducing noise and increasing resolution in magnetic heads.
In typical magnetic recording systems, magnetic data is converted to electrical signals using a magnetoresistive (MR) element, possibly of the spin-valve type. The basic structure of MR elements and of reproduction heads employed therein is shown in Jap. Unexamined Pat. Appl. Pub. No. H5-114119, for example. An MR element is typically disposed in such a way as to lie between magnetic shields which comprise a soft magnetic component. Furthermore, in systems utilizing MR elements, magnetic data is generally converted to electrical signals by the movement of the magnetization in the magnetization-free layer according to the magnetic field from the medium. In this process, magnetic domain structure in the magnetization-free layer causes large fluctuations in reproduction output and causes errors when reading the magnetic data. Therefore, a structure incorporating a magnetic field to control magnetic domain may be applied by an adjacent permanent magnet in order to prevent such errors.
One contributing factor which aids in determining the resolution of reproduction head structures of this kind is the magnetic shield gap, which is the distance between the magnetic shields on the medium facing side of the structure. Since the MR element is disposed between magnetic shields, current approaches reduce the thickness of the MR element in order to increase the resolution. However, the limit for reducing the thickness of the element is estimated to be around 20 nm, presently.
In order to break through this limit, a structure was proposed in FIG. 2B of Jap. Unexamined Pat. Appl. Pub. No. 2003-77107 in which only a magnetic flux guide is exposed on the medium facing surface. In this structure, the MR element is separated from the medium facing surface, and only a magnetic flux guide, which is connected to the MR element, is exposed up to the medium facing surface. This mitigates constraints in terms of the thickness of the MR element, and the shield gap at the medium facing surface can be freely set. Therefore, it is possible to improve the reproduction resolution in the head movement direction.
However, the structures disclosed in Jap. Unexamined Pat. Appl. Pub. Nos. H5-114119 and 2003-77107 carry a greater risk of error due to fluctuations in the reproduction output. This is because the magnetic field for controlling the magnetic domain is absorbed in the vicinity of the medium facing surface where the shield gap is narrow and therefore becomes weaker, and a magnetic domain structure is readily formed in the magnetic flux guide. In addition, it is only the reproduction resolution in the head movement direction which is improved with these structures, and it is not possible to improve the reproduction resolution in the direction away from tracks which are perpendicular to the head movement direction (the cross-track direction).
Therefore, a magnetic head design which alleviates the constraints and problems with prior art designs which allows for improvements in the reproduction resolution regardless of the thickness of the MR element and without increasing fluctuations in reproduction output would be very beneficial.